NATIONAL SENIOR CERTIFICATE GRADE 12

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1 NTIONL SENIOR ERTIFITE GRE 12 MEHNIL TEHNOLOGY NOVEMER 2017 MRKS: 200 TIME: 3 hours This question paper consists of 15 pages and a 4-page formula sheet.

2 Mechanical Technology 2 E/November 2017 INSTRUTIONS N INFORMTION 1. This question paper consists of TEN questions. 2. Write your centre number and examination number in the spaces provided on the NSWER OOK. 3. Read LL the questions carefully. 4. nswer LL the questions. 5. Number the answers correctly according to the numbering system used in this question paper. 6. Start EH question on a NEW page. 7. Show LL calculations and units. Round off LL answers to TWO decimal places. 8. andidates may use non-programmable, scientific calculators and drawing instruments. 9. Take the value of gravitational force as 10 m/s ll dimensions are in millimetres, unless stated otherwise in the question. 11. formula sheet for your use is attached to this question paper. 12. Write neatly and legibly. 13. Use the guidelines below to assist you in managing your time. QUESTION ONTENT MRKS TIME (minutes) 1 Multiple-choice questions Safety Tools and Equipment Materials Terminology Joining Methods Forces Maintenance Systems and ontrol Turbines TOTL

3 Mechanical Technology 3 E/November 2017 QUESTION 1: MULTIPLE-HOIE QUESTIONS Various options are provided as possible answers to the following questions. hoose the answer and write only the letter ( ) next to the question number ( ) in the NSWER OOK, for example efore operating the centre lathe, you should remove all safety guards. know where the ON/OFF switch is. remove the compound slide. oil the area surrounding the machine. (1) 1.2 Which ONE of the following safety rules applies to MIG/MGS welding equipment? Remove oil from the electrode wire. The welding pistol must be well lubricated. The electrical leads must be well insulated. Make sure that the gas flow is set to maximum. (1) 1.3 What is the function of a gas analyser? gas analyser analyses inlet gases. fuel gases. oil gases. exhaust gases. (1) 1.4 Which measuring equipment is used to measure the indentation of a rinell hardness test? Vernier calliper Microscope Ruler Micrometer (1) 1.5 What will be the result when steel is heated past the 2 line? Grain structure will be at its smallest. It will become brittle. It will start losing magnetism. It will become a stronger magnet. (1) 1.6 Which ONE of the following is a property of ferrite? rittle Hard Very hard Soft (1)

4 Mechanical Technology 4 E/November What is the magnitude of the included angle of the isometric V-screw thread? (1) 1.8 Which indexing method can be used to mill seven equal divisions with the help of a 40 : 1 dividing head? ngular indexing Rapid indexing Simple indexing Helical indexing (1) 1.9 How are welding defects observed when an X-ray test is performed on a welding joint? efects are visible on the weld. visible on film. determined by sound. visible on an oscilloscope screen. (1) 1.10 What is the purpose of performing an ultrasonic test on a welded joint? To detect internal defects. internal and external defects. external surface defects. all kinds of defects. (1) 1.11 What do you understand by the term strain in materials? Strain is the ratio between the change in length and the original length. load and the area. stress and the length. stress and the area. (1)

5 Mechanical Technology 5 E/November What does point represent in the graph in FIGURE 1.12 below regarding the stress and strain? Stress Strain FIGURE 1.12 The limit of proportionality The break stress The maximum stress The stretch limit (1) 1.13 What is understood by the term Young's modulus of elasticity? The force value required to produce a unit area in a tensile test specimen The ratio between stress and strain in a metal, provided that the limit of elasticity is not exceeded measurement of the extension or contraction of material due to the load experienced ratio of the deformation due to the application of an external force (1) 1.14 What is understood by the term flashpoint regarding oil? The lowest temperature at which the oil gives off vapours which can expand The lowest temperature at which the oil gives off vapours which can ignite The highest temperature at which the oil gives off vapours which can expand The highest temperature at which the oil gives off vapours which can ignite (1) 1.15 What does the abbreviation EP stand for regarding the lubrication of parts? External pressure Extreme pressure Extra pressure Excessive pressure (1)

Mechanical Technology 6 E/November 2017 1.16 What can be done to increase the pressure in a gas?

6 Mechanical Technology 6 E/November What can be done to increase the pressure in a gas? Increase the volume Increase the temperature and the volume ecrease the temperature ecrease the volume (1) 1.17 What will be the belt speed of a belt drive system if the driven pulley rotates at 500 r/min and has a diameter of 200 mm? 52,4 m.s -1 5,24 m.s m.s m.s -1 (1) 1.18 etermine the thickness of a parallel key if the diameter of the shaft is 72 mm: 21 mm 12 mm 18 mm 108 mm (1) 1.19 supercharger is driven by steam. a belt drive. exhaust gases. inlet gases (1) 1.20 Identify the type of turbine in FIGURE 1.20 below regarding the principle of operation. FIGURE 1.20 Reaction turbine Extracting turbine Impulse turbine Induction turbine (1) [20]

7 Mechanical Technology 7 E/November 2017 QUESTION 2: SFETY 2.1 ll personal and environmental safety rules are applicable when a surface grinder is used. State THREE safety rules which are only applicable while the surface grinder is in operation. (3) 2.2 Give TWO reasons why the pressure gauge of a hydraulic press must be tested regularly. (2) 2.3 State THREE important safety precautions that should be observed before MIG/MGS welding is done. (3) 2.4 State TWO safety rules that must be taken into consideration for the safe handling of coil spring compressors. (2) [10] QUESTION 3: TOOLS N EQUIPMENT 3.1 Explain how a voltmeter and an ammeter are connected to a circuit. (2) 3.2 State FOUR uses of a multimeter. (4) 3.3 dry compression test on an internal combustion engine indicated a very low reading at cylinder 1. wet compression test indicated a higher reading at cylinder 1. What conclusion can be made regarding these readings? (2) 3.4 escribe the purpose of the following tests: eam-bending test (2) ylinder leakage test (2) [12]

8 Mechanical Technology 8 E/November 2017 QUESTION 4: MTERILS 4.1 Name TWO properties of EH of the following structures of steel: ementite (2) Ferrite (2) 4.2 FIGURE 4.2 below is a diagram that shows the heating process of carbon steel. nswer the questions that follow. Temperature ( ) arbon content (%) FIGURE Identify the diagram shown in FIGURE 4.2. (2) Label E. (5) What is the lower critical temperature for steel with a carbon content of 0,83%? (2) [13]

1.2 Included screw-thread angle (1) 5.1.3 Screw-thread pitch (1) 5.1.4 Screw-thread crest (1) 5.1.5 Screw-thread flanks (1) 5.

9 Mechanical Technology 9 E/November 2017 QUESTION 5: TERMINOLOGY 5.1 Neatly sketch and label an isometric V-screw thread to indicate the following screw thread terminology on: rest, major or outside diameter (1) Included screw-thread angle (1) Screw-thread pitch (1) Screw-thread crest (1) Screw-thread flanks (1) 5.2 Identify the milling processes indicated in FIGURES and below FIGURE (1) FIGURE (1) 5.3 gear with 22 teeth has to be machined on a milling machine. alculate the required indexing. (6)

Mechanical Technology 10 E/November 2017 5.4 nswer the questions below with reference to the drawing of the dividing head in FIGURE 5.4 below. FIGURE 5.4 5.4.1 What is the function of sector arms and H?

10 Mechanical Technology 10 E/November nswer the questions below with reference to the drawing of the dividing head in FIGURE 5.4 below. FIGURE What is the function of sector arms and H? (2) What is the function of index plate G? (2) What is the function of index pin? (2) What is the ratio between worm gear E and gear? (2) 5.5 gear with 94 teeth and a module of 3 has to be machined on a milling machine. alculate the: Pitch-circle diameter (P) (3) Outside diameter (2) edendum (2) utting depth (2) [30]

11 Mechanical Technology 11 E/November 2017 QUESTION 6: JOINING METHOS 6.1 State TWO causes of undercutting in an arc-welded joint. (2) 6.2 How would you prevent slag inclusion in an arc-welded joint? (2) 6.3 escribe how the liquid dye penetration test is done on a welded joint. (4) 6.4 Name THREE advantages of the use of MIG/MGS welding rather than arc welding. (3) 6.5 State TWO functions of the gas flow meter. (2) 6.6 Label the parts E in the illustration of the MIG/MGS-welding process in FIGURE 6.6 below. FIGURE 6.6 (5) 6.7 What is the purpose of the shielding gas in the MIG/MGS welding process? (2) 6.8 Why must the earth cable be properly connected to the parent metal? (2) 6.9 Name THREE types of gases used for MIG/MGS welding. (3) [25]

12 Mechanical Technology 12 E/November 2017 QUESTION 7: FORES 7.1 Four forces of 100 N, 200 N, 300 N and 400 N respectively are acting on the same point, as shown in FIGURE 7.1 below. etermine, by means of calculations, the magnitude and direction of the resultant force for the system of forces in FIGURE 7.1. FIGURE 7.1 (13) 7.2 load of 40 kn is exerted onto a solid brass bar with a diameter of 56 mm. The original length of the bar is 0,85 m. Young's modulus for brass is 90 GPa. alculate the: Stress in the bar (5) Strain (3) hange in length (3) 7.3 FIGURE 7.3 below shows a uniform beam that is supported by two vertical supports, and. uniformly distributed force of 80 N/m is exerted over the whole length of the beam. etermine, by means of calculations, the magnitudes of the reactions in supports and. FIGURE 7.3 (6) [30]

13 Mechanical Technology 13 E/November 2017 QUESTION 8: MINTENNE 8.1 Explain the term pour point with regard to oils. (2) 8.2 State THREE advantages of the use of cutting fluid on a centre lathe. (3) 8.3 What does the abbreviation TF stand for with regard to motor oils? (2) 8.4 Name the THREE main parts of a clutch assembly. (3) 8.5 State THREE results of a stretched chain on a chain drive system. (3) 8.6 State TWO causes of belt slip on a belt drive system. (2) [15] QUESTION 9: SYSTEMS N ONTROL 9.1 FIGURE 9.1 below shows a gear drive system. river gear on the shaft of an electric motor has 30 teeth and mesh with gear with 40 teeth on a counter shaft. On the counter shaft is another driver gear,, with 20 teeth that mesh with gear with 60 teeth on a second counter shaft. The second counter shaft has driver gear E with 50 teeth, which drive gear F with 70 teeth on the output shaft. Electrical motor ounter shaft E 60 ounter 50 shaft 20 F 70 Output shaft FIGURE 9.1 alculate the: Rotation frequency of the output shaft if the electric motor rotates at r/min (3) Velocity ratio between the input and output shaft (2)

Mechanical Technology 14 E/November 2017 9.2 FIGURE 9.2 below shows a belt drive system with a 260 mm driver pulley. The belt speed of the system is 32 m.s -1.

14 Mechanical Technology 14 E/November FIGURE 9.2 below shows a belt drive system with a 260 mm driver pulley. The belt speed of the system is 32 m.s -1. The tensile force in the slack side is 140 N and the ratio between the force in the tight side and the force in the slack side is 2,5. T 2 T 1 FIGURE 9.2 N R =? r/min R = 260 mm alculate the: Rotation frequency of the driven pulley in r/min (revolutions per minute) (3) Tensile force in the tight side of the belt used in this system (2) Power transmitted (3) 9.3 hydraulic system is used to lift a machine. The specifications of the system are presented diagrammatically in FIGURE 9.3 below. FIGURE 9.3 alculate the: Fluid pressure in the hydraulic system when in equilibrium (4) istance L that Piston will move with one stroke of Piston (4)

Mechanical Technology 15 E/November 2017 9.4 What is the purpose of traction control in a motor vehicle? (2) 9.5 Why is a safety belt in a motor vehicle regarded as an active safety feature?

15 Mechanical Technology 15 E/November What is the purpose of traction control in a motor vehicle? (2) 9.5 Why is a safety belt in a motor vehicle regarded as an active safety feature? (2) [25] QUESTION 10: TURINES 10.1 Name ONE type of impulse water turbine. (1) 10.2 efine the run-away speed of a water turbine. (2) 10.3 FIGURE 10.3 below shows a water turbine driving a generator. nswer the questions that follow. FIGURE Identify the type of turbine shown in FIGURE (1) Label parts F. (6) State THREE advantages of the turbine shown in FIGURE (3) 10.4 State the main function of turbochargers and superchargers used on internal combustion engines. (2) 10.5 Name the type of compressor used in a turbocharger. (1) 10.6 How is a turbocharger driven? (1) 10.7 State ONE advantage of a turbocharger. (1) 10.8 State TWO advantages of a steam turbine. (2) [20] TOTL: 200

16 Mechanical Technology 1 E/November ELT RIVES 1.1 N dr dr = N dn dn FORMUL SHEET πn 1.2 elt speed = where N is in r/min 60 π ( + t ) N 1.3 elt speed = (t = belt thickness) elt mass = area length density ( = thickness width) 1.5 Speed ratio = diameter of driven pulley diameter of driver pulley 1.6 elt length (flat belt) = [( + d) 1,57] + 2 centre distance 2 2 π( + d ) ( d ) 1.7 Open-belt length = + + 2c 2 4c 2 2 π( + d ) ( + d ) 1.8 rossed-belt length = + + 2c 2 4c 1.9 Ratio of tight side to slack side T = T Power (P) = (T1 T2 ) π N 60 where N is in r/min T = force in the tight side T 1 2 = force in the slack side T T 1 2 = effective force (T ) e 1.11 Power (P) = (T1 T2 ) V where V = belt speed in m/s 2 π N T 1.12 Power ( P ) = where N is in r/min T1 Width = permissible tensile force

17 Mechanical Technology 2 E/November STRESS N STRIN force F 2.1 Stress = or (σ = ) area 2.2 change in length (ΔL) Strain (ε ) = original length ( L) 2.3 stress σ Young' s modulus ( E ) = or ( ) strain ε 2.4 πd 2 rea of a round bar = = rea of a pipe = = π ( 2 2 d ) 2.6 rea of a square bar = = L 2 or = L 3. HYRULIS force (F) Pressure (P) = area () 3.2 Volume = (cross-sectional area) stroke length 3.3 Work done = force distance 4. KEYS N KEYWYS 4.1 diameter of shaft Width of key= Thickness of key = diameter of shaft Length of key = 1,5 diameter of shaft 4.4 Standard taper for taper key: 1 in 100 or 1 : 100

18 Mechanical Technology 3 E/November LEVERS Mechanical advantage (M) = Velocity ratio = input movement output movement load (W) effort (F) 5.3 Input movement (IM) = effort distance moved by effort 5.4 Output movement (OM) = load distance moved by load 6. GER RIVES 6.1 N dr dr = N dn dn 6.2 Power ( P ) = 2 π N T Gear ratio = product of the number of teeth on the driven gears product of the number of teeth on the driver gears Ninput 6.4 = N output product of the number of teeth on the driven gears product of the number of teeth on the driver gears 6.5 Torque = force radius 6.6 Torque transmitted = gear ratio input torque 6.7 pitch-circlediameter (P) Module (m) = number of teeth (T) 6.8 N 1T1 = N 2T2 6.9 Pitch -circlediameter (P) circular pitch (P) number of = π teeth (T) 6.10 Pitch -circlediameter (P) = m T 6.11 Outside diameter (O) = m(t + 2) 6.12 Outside diameter (O) = pitch-circle diameter (P) + 2 module 6.13 ddendum = module (m) 6.14 edendum = 1,157 m or edendum = 1,25 m

19 Mechanical Technology 4 E/November utting depth = 2,157 m or utting depth = 2,25 m 6.16 learance = 0,157 m or learance = 0,25 m 6.17 ircular pitch (P) = m π 6.18 entre distance between gear and 7. SREW THRES = (P) 2 + (P) Pitch diameter = outside diameter ½pitch 7.2 Pitch circumference = π pitch diameter 7.3 Lead = pitch number of starts 7.4 Height of screw thread = 0,866 pitch 7.5 epth of screw thread = 0,613 pitch 8. INEXING 8.1 incinnati dividing head table for milling machine incinnati Index Plate Side Side Indexing = n (where n = number of divisions)

GRAAD 12 NATIONAL SENIOR CERTIFICATE GRADE 12

GRAAD 12 NATIONAL SENIOR CERTIFICATE GRADE 12 GR 12 NTIONL SENIOR ERTIFITE GRE 12 MEHNIL TEHNOLOGY EXEMPLR 2014 MRKS: 200 TIME: 3 hours This question paper consists of 18 pages and a 3-page formula sheet. opyright reserved Mechanical Technology 2